# Protocols for Node.JS [](https://travis-ci.org/wuhkuh/protocol) [](https://greenkeeper.io/)
### Create and edit network protocols the easy way. 
No more bitwise logic - give it a template and let it do the work for you.
* Installation
* Example
* API
* Supported Node versions
* License
## Installation
```js
npm install protocol --save
```
## Example
```js
const Protocol = require('protocol')
const myProtocol = new Protocol({
header: [{
firstBit: { bitLength: 1 },
secondBit: { bitLength: 1 }
}],
payloadLength: { bitLength: 4 },
payload: { byteLength: 'payloadLength', encoding: 'utf8' }
})
/*
* 0x90 is hex for '1001 0000'
* firstBit: 1, secondBit: 0, payloadLength: 4 (bitwise 0100)
* payload: 'abcd' (0x61 to 0x64)
*/
myProtocol.parse(Buffer.from([0x90, 0x61, 0x62, 0x63, 0x64]))
/*
* '0 1 0010 00' to hex -> 0x48
* 'bd' -> 0x62, 0x64
* result: Buffer <0x48, 0x62, 0x64>
*/
myProtocol.generate({
header: {
firstBit: 0,
secondBit: 1
},
payloadLength: 2, // this has to be set explicitly!
payload: 'bd'
})
```
View the API or the example folder in this project's repository for a closer look.
> Good practice:
> Create a protocol in a separate file and share it between clients.
## API
* Protocol
* protocol#generate()
* protocol#parse()
---
### `Protocol(schema)`
`Protocol` is the exposed class. Create it by using `new Protocol(schema)`.
The `schema` parameter is an object with the following notation:
```js
const schema = {
header: [{
firstBit: { bitLength: 1 },
secondBit: { bitLength: 1 }
}],
payloadLength: { bitLength: 4 },
payload: { byteLength: 'payloadLength' }
}
```
Protocols are read in top-to-bottom order, with the input in Big Endian (network order as
defined in RFC 1700). This means that a Buffer will be parsed and generated from left to right.
The current supported options are:
* `bitLength` in amount of bits, or a string that points to another key when variable.
* `byteLength` in amount of bytes, or a string that points to another key when variable.
* `dict` as an object containing values for parsing and generating.
* `encoding` as a string containg the required encoding.
If not present, parsing returns a Buffer.
* `type` as a class, only supporting Boolean at this moment.
This converts outputs to Booleans (all non-zeros are true).
---
### `Protocol.generate(object)`
This method generates a Buffer from an Object. It starts with dictionary translation and
type handling, followed by concatenation and outputting a single Buffer.
* `object: Object`
Input object that shall be translated to a Buffer using a Protocol.
If there is no encoding given during generation of a Buffer, it uses UTF-8.
If the input already contains a value of type Buffer, it will retain this Buffer.
When a length is variable and points to key `x`, `x` does not automatically get a value assigned.
__This has to be set explicitly!__
---
### `Protocol.parse(buffer)`
This method generates an Object from a Buffer. It splits the individual bits and bytes,
followed by type handling and dictionary translation.
* `buffer: Buffer`
Input buffer that shall be translated to an Object using a Protocol.
If there is no encoding given during parsing of a Buffer, it will retain this Buffer.
## Supported Node versions
| Version | Supported until |
| --------- | :---------------: |
| Node v7 | 2017-06-01 |
| Node v8 | 2019-12-31 |
## License
MIT